U.S. patent application number 13/272335 was filed with the patent office on 2012-05-03 for wood fiber board and manufacturing method thereof.
Invention is credited to Makoto KIMURO, Hiromasa SINKAI, Kenji TAKESHITA.
Application Number | 20120108706 13/272335 |
Document ID | / |
Family ID | 44719487 |
Filed Date | 2012-05-03 |
United States Patent
Application |
20120108706 |
Kind Code |
A1 |
KIMURO; Makoto ; et
al. |
May 3, 2012 |
WOOD FIBER BOARD AND MANUFACTURING METHOD THEREOF
Abstract
Provided is a wood fiber board, and a production method thereof,
such that the wood fiber board contains no phenolic resin, is
simple to produce, and exhibits flexural strength and water
resistance comparable to those of wood fiber boards produced by
incorporating a phenolic resin. The wood fiber board of the present
invention has only wood fibers; a polyacrylamide resin being an
amphoteric-ionic resin, which has monomers having cationic groups
and monomers having anionic groups at a ratio of 7:3 to 3:7 on a
mole ratio basis, and which has a molecular weight ranging from
800,000 to 3,000,000; and cationic paraffin. A method of producing
a wood fiber board of the present invention involves preparing a
slurry to a solids concentration ranging from 2 to 3 wt % and pH of
3 to 5, and adding only the polyacrylamide resin and paraffin to
the slurry.
Inventors: |
KIMURO; Makoto; (Nagoya-shi,
JP) ; SINKAI; Hiromasa; (Chita-shi, JP) ;
TAKESHITA; Kenji; (Tokai-shi, JP) |
Family ID: |
44719487 |
Appl. No.: |
13/272335 |
Filed: |
October 13, 2011 |
Current U.S.
Class: |
524/13 ;
264/331.16 |
Current CPC
Class: |
Y10T 428/249925
20150401; Y10T 428/31986 20150401; D21J 1/18 20130101 |
Class at
Publication: |
524/13 ;
264/331.16 |
International
Class: |
C08L 97/02 20060101
C08L097/02; B29C 43/52 20060101 B29C043/52 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 29, 2010 |
JP |
JP2010-244404 |
Claims
1. A wood fiber board comprising only wood fibers, a polyacrylamide
resin and paraffin, wherein the polyacrylamide resin is an
amphoteric-ionic resin, contains monomers having cationic groups
and monomers having anionic groups at a ratio of 7:3 to 3:7, on a
mole ratio basis, and has a molecular weight ranging from 800,000
to 3,000,000, the paraffin is cationic, the polyacrylamide resin
content ranges from 0.1 to 0.6 wt % with respect to total solids of
the wood fibers, the paraffin content ranges from 0.2 to 0.9 wt %
with respect to total solids of the wood fibers, and the wood
fibers are tangled with one another, and the polyacrylamide resin
and the paraffin fill gaps between the wood fibers.
2. The wood fiber board according to claim 1, wherein the wood
fibers are fibers obtained through the steaming and fibrillating of
wood and scrap wood from scrap wood fiber boards, and the content
of fibers obtained through steaming and fibrillating of scrap wood
from scrap wood fiber boards is less than 10 wt % with respect to
total solids of the wood fiber board.
3. A method of producing a wood fiber board, the method comprising
the steps of: producing a slurry by dispersing wood fibers in
water; producing a mat by adding only paraffin and an acrylamide
resin to the obtained slurry and performing sheet forming; and
heat-pressing the obtained mat, and wetting or
humidity-conditioning the mat, followed by curing, wherein in the
step of producing a slurry, the slurry is prepared to a solids
concentration of 2 to 3 wt % and pH of 3 to 5, and in the step of
producing a mat, an amphoteric polyacrylamide resin being an
amphoteric-ionic resin, which contains monomers having cationic
groups and monomers having anionic groups at a ratio of 7:3 to 3:7
on a mole ratio basis, and which has a molecular weight ranging
from 800,000 to 3,000,000, is added 0.1 to 0.6 wt % with respect to
total solids of the wood fibers, and cationic paraffin is added 0.2
to 0.9 wt % with respect to total solids of the wood fibers.
4. The method of producing a wood fiber board according to claim 3,
wherein the wood fibers are fibers obtained through steaming and
fibrillating of wood and scrap wood from scrap wood fiber boards,
and the content of fibers obtained through steaming and
fibrillating of scrap wood from scrap wood fiber boards is less
than 10 wt % with respect to total solids of the wood fiber board.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a wood fiber board that is
used in vehicle interiors, building materials, furniture and the
like.
[0003] 2. Description of the Related Art
[0004] Conventionally, wood is made into wood chips using a crusher
or the like, the obtained wood chips are steamed and are
fibrillated using a refiner or the like, to produce a fiber board
out of the wood fibers. For instance, Japanese Patent Application
Publication No. 2001-3300 discloses a method of manufacturing a
wood fiber board by forming a sheet out of a starting material
slurry in which wood fibers are dispersed, dewatering the formed
sheet by suction, using a cylinder sheet-forming machine, followed
by forming and drying, to produce thereby a wood fiber board.
[0005] The production method set forth in Japanese Patent
Application Publication No. 2001-3300 requires a binder for binding
fibers to each other. Japanese Patent Application Publication No.
2001-3300 discloses, starch thickeners, phenolic resins, melamine
resins, urea resins and the like as examples of binders. Among
those, phenolic resins have been used from the viewpoint of
strength and water resistance.
[0006] However, concerns about the odor and volatile organic
compounds released by phenolic resins have become a concern against
the background of growing environmental awareness in recent years.
Desirably, therefore, wood fiber boards should contain no phenolic
resins.
[0007] The applicants had already filed Japanese Patent Application
Publication No. 2010-121058 relating to a phenolic resin-free wood
fiber board.
[0008] The wood fiber board of Japanese Patent Application
Publication No. 2010-121058 is produced using an acrylic resin and
an epoxy resin containing no bisphenol A, instead of using a
phenolic resin. Therefore, the board has no phenol odor, and the
release of volatile organic compounds is extremely small.
[0009] The wood fiber board of Japanese Patent Application
Publication No. 2010-121058, however, utilizes two types of resin,
namely an acrylic resin and an epoxy resin containing no bisphenol
A, as binders, and requires moreover paraffin in order to enhance
water resistance. The board is thus troublesome in terms of
equipment and operations, which should be streamlined.
SUMMARY OF THE INVENTION
[0010] Therefore, it is an object of the present invention to
provide a wood fiber board, and a production method thereof, such
that the wood fiber board contains no phenolic resin, is simple to
produce, and boasts flexural strength and water resistance
comparable to those of wood fiber boards produced by incorporating
a phenolic resin.
[0011] The present invention provides a wood fiber board that
comprises only wood fibers, a polyacrylamide resin and paraffin. In
the wood fiber board of the present invention, the polyacrylamide
is an amphoteric-ionic resin, contains monomers having cationic
groups and monomers having anionic groups at a ratio of 7:3 to 3:7,
on a mole ratio basis, and has a molecular weight ranging from
800,000 to 3,000,000; and the paraffin is cationic. The
polyacrylamide resin content ranges from 0.1 to 0.6 wt % with
respect to total solids of the wood fibers; and the paraffin
content ranges from 0.2 to 0.9 wt % with respect to total solids of
the wood fibers. The wood fibers are tangled with one another, and
the polyacrylamide resin and the paraffin fill gaps between the
wood fibers.
[0012] The wood fiber board of the present invention may contain
fibers obtained through steaming and fibrillating of scrap wood
from wood fiber boards, in an amount smaller than 10 wt % with
respect to total solids of the wood fiber board. Effective
utilization of scrap wood can be promoted thus by incorporating
fibers obtained out of scrap wood from scrap wood fiber boards.
[0013] The present invention provides a method of producing a wood
fiber board. The method of producing a wood fiber board of the
present invention has the steps of: producing a slurry by
dispersing wood fibers in water; producing a mat by adding only
paraffin and an acrylamide resin to the obtained slurry and
performing sheet forming; and heat-pressing the obtained mat, and
wetting or humidity-conditioning the mat, followed by curing. In
the step of producing a slurry, the slurry is prepared to a solids
concentration of 2 to 3 wt % and pH of 3 to 5. In the step of
producing a mat, an amphoteric polyacrylamide resin being an
amphoteric-ionic resin, which contains monomers having cationic
groups and monomers having anionic groups at a ratio of 7:3 to 3:7
on a mole ratio basis, and which has a molecular weight ranging
from 800,000 to 3,000,000, is added 0.1 to 0.6 wt % with respect to
total solids of the wood fibers, and cationic paraffin is added 0.2
to 0.9 wt % with respect to total solids of the wood fibers. In the
method of producing a wood fiber board of the present invention,
there may be incorporated fibers obtained through steaming and
fibrillating of scrap wood from scrap wood fiber boards, in an
amount less than 10 wt % with respect to total solids of the wood
fiber board.
[0014] The wood fiber board of the present invention comprises only
wood fibers, a polyacrylamide resin and paraffin, and hence
comprises no phenolic resin. Also, the wood fibers are tangled with
one another, and the polyacrylamide resin and the paraffin fill
gaps between the wood fibers. Therefore, the wood fiber board
boasts flexural strength and water resistance comparable to those
of wood fiber boards produced by incorporating a phenolic resin. In
the method of producing a wood fiber board of the present
invention, a polyacrylamide resin alone is used as binder.
Therefore, the wood fiber board is simple to produce and boasts
flexural strength and water resistance comparable to those of wood
fiber boards produced by incorporating a phenolic resin.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Specific embodiments of the present invention are explained
below.
[0016] The wood fiber board of the present invention comprises only
wood fibers, a polyacrylamide resin and paraffin.
[0017] The wood fibers of the present invention are obtained by
chipping wood into wood chips using a crusher or the like, steaming
the obtained wood chips, and fibrillating the steamed chips using a
refiner pulper. The wood fibers may also contain wood fibers in the
form of fibers obtained through steaming and fibrillating of scrap
wood from scrap wood fiber boards.
[0018] The polyacrylamide resin is amphoteric, contains monomers
having cationic groups and monomers having anionic groups at a
ratio ranging from 7:3 to 3:7, on a mole ratio basis, and has a
molecular weight ranging from 800,000 to 3,000,000. Examples of
monomers having cationic groups include, for instance, a
2-(meth)acryloyloxyethyltrimethyl ammonium salt or
2-(meth)acryloylaminoethyltrimethyl ammonium salt, a
diallyldimethyl ammonium salt, a diallylamine compound or the like.
Examples of monomers having anionic groups include, for instance,
.alpha.,.alpha.-unsaturated carboxylic acids and salts thereof. In
the amphoteric polyacrylamide resin, the ratio of the monomers
having cationic groups and monomers having anionic groups is set to
range from 7:3 to 3:7, on a mole ratio basis. The wood fiber and
the paraffin can be complemented as a result in the production
process. In the production process of the wood fiber board,
specifically, the wood fibers are firstly dispersed in water, to
yield a slurry having a pH from 3 to 5, and paraffin and an
acrylamide resin are then added to the slurry. Herein, the surface
potential of the wood fiber is anionic, while the below-described
paraffin is cationic. Thus, the amphoteric polyacrylamide resin can
complement both the wood fibers and the paraffin. Also, flocks can
be formed in the water having a pH ranging from 3 to 5 in which
wood fibers are dispersed, by setting the content ratio of the
monomers having cationic groups and the monomers having anionic
groups to range from 7:3 to 3:7, on a mole ratio basis. Therefore,
the wood fibers can be dewatered with good efficiency, and a mat of
the wood fiber board can be produced with good yield. Further,
paraffin can be complemented with good efficiency. The water
resistance of the wood fiber board is enhanced thereby. Also, the
molecular weight of the polyacrylamide resin ranges from 800,000 to
3,000,000, which results in a constant viscosity in the liquid
state. The wood fibers and the paraffin can be easily complemented
thereby. If the molecular weight of the polyacrylamide resin is
smaller than 800,000, the flocks that form upon complementation of
the wood fibers and the paraffin are small, and yield is poor. If
the molecular weight exceeds 3,000,000, formation of strong flocks
gives rise to uneven distribution of wood fibers, polyacrylamide
resin and paraffin inside the wood fiber board obtained after
dewatering. This may impair the flexural strength of the wood fiber
board.
[0019] Paraffin is cationic. Accordingly, paraffin can be easily
complemented by the amphoteric polyacrylamide resin. Also, the
surface potential of wood fibers is anionic, and hence paraffin
becomes readily fixed to the surface of the wood fiber.
[0020] The wood fiber board of the present invention contains 90 wt
% or more, with respect to total solids of the wood fiber board, of
fibers obtained through steaming and fibrillating of wood, contains
0.1 to 0.6 wt % of polyacrylamide resin with respect to total
solids of the wood fibers, and contains 0.2 to 0.9 wt % of paraffin
with respect to total solids of the wood fibers. The content of
fibers obtained through steaming and fibrillating of scrap wood
from scrap wood fiber boards can be smaller than 10 wt % with
respect to total solids of the wood fiber board. As the scrap wood
of the scrap wood fiber board there are preferably used parts of
wood fiber board, defective boards and the like that occur in a
production process, since this way the wastage of the production
process can be reduced.
[0021] The rationale for setting the content of polyacrylamide
resin to range from 0.1 to 0.6 wt % with respect to total solids of
the wood fibers is that a content smaller than 0.1 wt % results in
insufficient complementing of the wood fibers and the paraffin,
whereas a content of polyacrylamide resin in excess of 0.6 wt %
elicits no further effect for a higher cost. The reason for setting
the content of paraffin to be no greater than 0.2 to 0.9 wt % with
respect to total solids of the wood fibers is that the water
resistance of the wood fiber board is poor if the content of
paraffin is smaller than 0.2 wt %, while if the content exceeds 0.9
wt %, tangling among wood fibers becomes deficient, and the
flexural strength of the wood fiber board is impaired.
[0022] The method of producing a wood fiber board of the present
invention comprises the steps of: producing a slurry by dispersing
wood fibers in water; producing a mat by adding only paraffin and
an acrylamide resin to the obtained slurry and performing sheet
forming; and heat-pressing the obtained mat, and wetting or
humidity-conditioning the mat, followed by curing.
[0023] In the step of producing a slurry by dispersing wood fibers
in water, wood is crushed, and is steamed and fibrillated in a
fibrillating machine such as a refiner, and the wood fibers
obtained as a result are dispersed in water, to yield a slurry
having a solids concentration ranging from 2 to 3 wt % and a pH
ranging from 3 to 5. The wood fibers may be produced by using
concomitantly wood and scrap wood from scrap wood fiber boards. The
solids concentration of the slurry is set to range from 2 to 3 wt %
since a solids concentration ranging from 2 to 3 wt % favors
dispersion of wood fibers in water. If the solids concentration of
the slurry exceeds 3 wt %, the wood fibers fail to be dispersed
uniformly, while a substantial amount of water is required at a
solids concentration lower than 2 wt %. The reason for setting the
pH of the slurry to range from 3 to 5 is that wood fibers and
paraffin are complemented with good efficiency by an amphoteric
polyacrylamide resin containing monomers having cationic groups and
monomers having anionic groups at a ratio of 7:3 to 3:7, on a mole
ratio basis. Also, flocks can be formed with good efficiency for a
pH range of the polymer ranging from 3 to 5.
[0024] In the step of producing a mat by adding only paraffin and
an acrylamide resin to the obtained slurry and performing sheet
forming, there is added an amphoteric polyacrylamide resin
containing monomers having cationic groups and monomers having
anionic groups at a ratio of 7:3 to 3:7, on a mole ratio basis, the
resin having a molecular weight ranging from 800,000 to 3,000,000,
and there is added paraffin, which is cationic. The paraffin and
the polyacrylamide resin may be added simultaneously.
Alternatively, the paraffin may be added first, followed by
addition of the polyacrylamide resin. Addition is performed in such
a manner that the paraffin ranges from 0.2 to 0.9 wt % with respect
to total solids of the wood fibers and the polyacrylamide resin
ranges from 0.1 to 0.6 wt % with respect to total solids of the
wood fibers. The proportions of paraffin and polyacrylamide resin
with respect to the wood fibers are all values on a solids basis.
The rationale for these addition amounts are as described above.
The obtained slurry is run off on a wire mesh, and the rear face of
the wire mesh is vacuum-dewatered, to form a mat. Through such
sheet-forming, wood fibers become disposed in such a manner that
the longitudinal direction of the fibers is substantially
horizontal, on the front face side, while on the rear face side
(wire mesh side) the longitudinal direction of the fibers is
substantially vertical, on account of vacuum suction. The mesh
pattern of the wire mesh is transferred to the rear face of the
mat, and hence the rear face of the mat exhibits a rough surface.
The obtained mat is further dewatered, if necessary, by cold
pressing. After addition of the paraffin and the polyacrylamide
resin, the slurry may be stirred while the slurry runs off on the
wire mesh.
[0025] The obtained mat is heat-pressed. Heat pressing is performed
by three-stage pressing that involves pressing at a temperature
ranging from 180 to 220.degree. C., and a pressing pressure of 40
kg/cm.sup.2 for 30 to 50 seconds, 8 to 10 kg/cm.sup.2 for 60 to 180
seconds, and 20 to 35 kg/cm.sup.2 for 60 to 90 seconds, in the case
of producing a 2.5 mm-thick wood fiber board. In this three-stage
pressing, the pressure is lowered in the second stage, and hence
the water vapor in the mat can escape readily. Mat puncturing is
thus prevented. The press machine used in the three-stage pressing
has an upper mold and a lower mold. Wire mesh or a perforated board
is laid, as a spacer, at the surface of the lower mold. Water
squeezed out of the mat is drained thereby out of the press
machine.
[0026] After pressing, the obtained wood fiber board is wetted or
humidity-conditioned, to adjust thereby the moisture content to a
desired moisture content, and the board is cured for a given lapse
of time, to yield thereafter the product.
[0027] Examples of the present invention are explained next.
[0028] Wood was crushed, and was steamed and fibrillated using a
refiner, to yield wood fibers. The wood fibers were dispersed in
water, to yield a slurry having a solids concentration of about 2
wt % and a pH ranging from 3 to 5. To the obtained slurry there
were added an emulsion of cationic paraffin, and an amphoteric
polyacrylamide resin containing monomers having cationic groups and
monomers having anionic groups in a mole ratio of 6:4, the resin
having a molecular weight ranging from 1,700,000 to 2,000,000. The
slurry was stirred for one minute, was thereafter run off on a wire
mesh, and the rear face of the wire mesh was vacuum-dewatered, to
form a mat. Herein, paraffin was added so as to yield solids of 0.4
wt % with respect to total solids of the wood fibers, and a
polyacrylamide resin was added so as to yield solids of 0.1 wt %
with respect to total solids of the wood fibers. The obtained mat
was subjected to three-stage pressing at a temperature ranging from
180 to 220.degree. C., under 40 g/cm.sup.2 for 40 seconds, 8 to 10
kg/cm.sup.2 for 60 to 180 seconds and 30 kg/cm.sup.2 for 60 to 90
seconds. Humidity conditioning was performed thereafter, to yield a
wood fiber board of Example 1.
[0029] A wood fiber board of Example 2 was produced in the same way
as in Example 1, but herein there was added 0.4 wt % of
polyacrylamide resin with respect to total solids of the wood
fibers.
[0030] A wood fiber board of Example 3 was produced in the same way
as in Example 1, but herein there was added 0.6 wt % of
polyacrylamide resin with respect to total solids of the wood
fibers.
[0031] Scrap wood of Scrap wood fiber boards was crushed, and was
steamed and fibrillated using a refiner, to yield wood fibers. Wood
fibers resulting from steaming and fibrillating of wood, as well as
wood fibers resulting from steaming and fibrillating of scrap wood
from wood fiber boards, were added to water, in a weight ratio of
9:1. The wood fibers were dispersed in water, to yield a slurry
having a solids concentration of about 2 wt % and a pH ranging from
3 to 5. A wood fiber board was produced otherwise in the same way
as in Example 1, to yield a wood fiber board of Example 4.
[0032] Wood was crushed, and was steamed and fibrillated using a
refiner, to yield wood fibers. The wood fibers were dispersed in
water, to yield a slurry having a solids concentration of about 2
wt % and a pH ranging from 3 to 5. The slurry was run off on a wire
mesh, and the rear face of the wire mesh was vacuum-dewatered, to
form a mat. Herein, the slurry had no polyacrylamide resin,
paraffin, or phenolic resin added thereto. A wood fiber board was
produced otherwise in the same way as in Example 1, to yield a wood
fiber board of Comparative example 1.
[0033] Wood was crushed, and was steamed and fibrillated using a
refiner, to yield wood fibers. The wood fibers were dispersed in
water, to yield a slurry having a solids concentration of about 2
wt % and a pH ranging from 3 to 5. An emulsion of cationic paraffin
and a phenolic resin were added to the obtained slurry. A wood
fiber board was produced otherwise in the same way as in Example 1,
to yield a wood fiber board of Comparative example 2. Herein,
paraffin was added so as to yield solids of 0.4 wt % with respect
to total solids of the wood fibers, and the phenolic resin was
added so as to yield solids of 0.5 wt % with respect to total
solids of the wood fibers.
[0034] A wood fiber board of Comparative example 3 was produced in
the same way as in Example 1, but herein there was added 0.8 wt %
of polyacrylamide resin with respect to total solids of the wood
fibers.
[0035] The wood fiber boards obtained in Examples 1 to 4 and
Comparative examples 1 to 3 were measured for thickness, dry
density, moisture content, flexural strength and water absorption
rate. The results a given in Table 1. The thickness, dry density,
moisture content, flexural strength and water absorption rate were
measured according to JIS A 5905-2003.
TABLE-US-00001 TABLE 1 Example Example Example Example Comp. Comp.
Comp. 1 2 3 4 ex. 1 ex. 2 ex. 3 Thickness mm 2.33 2.32 2.29 2.32
2.26 2.35 2.36 Dry density 0.91 0.96 0.93 0.89 0.90 0.88 0.92
Moisture content % 9.0 5.6 6.6 8.5 6.8 7.6 6.8 Flexural strength
N/mm.sup.2 22.9 26.5 27.8 22.8 21.1 23.0 21.4 Water absorption rate
% 28.0 28.2 32.5 27.5 74.1 39.4 34.6
[0036] The flexural strength and water absorption rate in the wood
fiber boards of Examples 1 to 4 were superior to those of the wood
fiber board of Comparative example 1, which comprised wood fibers
alone, and were comparable to those of the wood fiber board of
Comparative example 2, which was produced through addition of a
phenolic resin. The wood fiber board of Comparative example 3, in
which 0.8 wt % of a polyacrylamide resin was added, with respect to
total solids of the wood fibers, exhibited poorer flexural strength
than the wood fiber board of Comparative example 2.
[0037] Embodiments of the present invention have been explained
above, but the present invention is not limited thereto, and can be
embodied in various ways without departing from the scope of the
invention as defined in the appended claims
[0038] As explained above, the present invention succeeds in
providing a wood fiber board, and a production method thereof, such
that the wood fiber board contains no phenolic resin, is simple to
produce, and boasts flexural strength and water resistance
comparable to those of wood fiber boards produced by incorporating
a phenolic resin.
* * * * *